Thermodynamic behaviour of some electrolytes in ethane-1,2-diol from −10 to +80 °C

1993 ◽  
Vol 71 (8) ◽  
pp. 1265-1272 ◽  
Author(s):  
Fulvio Corradini ◽  
Luigi Marcheselli ◽  
Lorenzo Tassi ◽  
Giuseppe Tosi ◽  
Salvatore Fanali
Keyword(s):  
Experimental Data ◽  
Dissociation Constant ◽  
Ion Pairs ◽  
Size Parameter ◽  
Equivalent Conductivity ◽  
Thermodynamic Behaviour ◽  
Informative Parameters ◽  
Ion Conductivities ◽  
Ion Size ◽  
Reference Electrolyte

Conductivities of the electrolytes NaBr, NaPi, HPi, NaBPh4, and Ph4PBr in ethane- 1,2-diol were determined in the −10 ≤ t ≤ +80 °C temperature range. The experimental data were analyzed by the Fuoss–Hsia equation, which provides further informative parameters such as the dissociation constant (K) of the ion pairs formed in solution, the limiting equivalent conductivity (Λ0), and the ion-size parameter (å). Thermodynamic behaviour of these electrolytes was derived from analysis of the K values. Single-ion conductivities were evaluated on the basis of the assumption of Ph4PBPh4 as reference electrolyte.

Solubility and Thermodynamic Transfer Functions of Cesium Dianilinetetraisothiocyanatochromate(III)

1998 ◽  
Vol 63 (3) ◽  
pp. 293-298
Author(s):  
Vladislav Holba
Keyword(s):  
Experimental Data ◽  
Isopropyl Alcohol ◽  
Transfer Functions ◽  
Butyl Alcohol ◽  
Aqueous Methanol ◽  
Gibbs Energies ◽  
Gibbs Energy Of Transfer ◽  
Energy Of Transfer ◽  
The Given ◽  
Reference Electrolyte

The solubilities of cesium dianilinetetraisothiocyanatochromate(III) in water as well as in aqueous methanol, isopropyl alcohol, tert-butyl alcohol and acetonitrile were measured as a function of temperature and solvent composition. The Gibbs energies, enthalpies and entropies of transfer of the salt from water to the given solvents have been evaluated from experimental data. The contribution of [Cr(C6H5NH2)2(NCS)4]- ion to the Gibbs energy of transfer of the investigated salt has been calculated using the tetraphenylarsonium tetraphenylborate (TATB) reference electrolyte assumption.

scholarly journals Interactions of Na+ Cations with a Highly Charged Fatty Acid Langmuir Monolayer: Molecular Description of the Phase Transition

2019 ◽  
Author(s):  
Adrien Sthoer ◽  
Eric Tyrode
Keyword(s):  
Phase Transition ◽  
Surface Charge ◽  
Surface Potential ◽  
Arachidic Acid ◽  
Ion Pairs ◽  
Theoretical Models ◽  
Langmuir Monolayer ◽  
Vibrational Sum Frequency Spectroscopy ◽  
Ion Size ◽  
Contact Ion Pairs

Vibrational sum frequency spectroscopy has been used to study the molecular properties upon compression of a highly charged arachidic acid Langmuir monolayer, which displays a first order phase transition plateau in the surface pressure - molecular area (p-A) isotherm. By targeting vibrational modes from the carboxylic acid headgroup, alkyl chain, and interfacial water molecules, information regarding the surface charge, surface potential, type of ion pair formed, and conformational order of the monolayer could be extracted. The monolayer in the liquid expanded phase is found to be fully charged until reaching the 2D-phase transition plateau, where partial reprotonation, as well as the formation of COO⎺ Na<sup>+ </sup>contact-ion pairs, start to take place. In the condensed phase after the transition, three headgroup species, mainly hydrated COO⎺, COOH, and COO⎺ Na<sup>+ </sup>contact-ion pairs could be identified and their proportions quantified. Comparison with theoretical models shows that despite the low ionic strengths used (i.e. 10 mM), the predictions from the Gouy Chapman model are only adequate for the lowest surface densities, when the surface charge does not exceed -0.1 C/m<sup>2</sup>. In contrast, a modified Poisson-Boltzmann (MPB) model that accounts for the steric effects associated with the finite ion-size, captures many of the experimental observables, including the partial reprotonation, and surface potential changes upon compression. The agreement highlights the importance of hydronium ion – carboxylate interactions, as well as the layer of sodium ions packed at the steric limit, for explaining the phase transition behavior. The MPB model, however, does not explicitly consider the formation of contact ion pairs with the sodium counterion. The experimental results provide a quantitative molecular insight that could be used to test potential extensions to the theory.

Conductimetric studies of ionic association of tetraalkylammonium halides in iso-propanol + water mixtures at 25 °C. Part II.

1988 ◽  
Vol 66 (7) ◽  
pp. 1720-1727 ◽  
Author(s):  
Auaz Ahmad Ansari ◽  
M. R. Islam
Keyword(s):  
Dielectric Constant ◽  
Association Constant ◽  
Ionic Association ◽  
Size Parameter ◽  
Solvent Interactions ◽  
Tetraalkylammonium Ions ◽  
Conductance Data ◽  
Electrical Conductivities ◽  
Ion Size ◽  
Tetraalkylammonium Halides

Electrical conductivities of Me4NBr, Et4NBr, Pr4NBr, Bu4NBr, and Bu4PBr have been measured in isopropanol + water (2-PrOH + H2O) mixtures covering the approximate range of dielectric constant (71.40 ≥ D ≥ 19.40) at 25 °C. The conductance data have been analysed by using the Fuoss-1978 (F78) conductance equation and the results compared with those obtained from the Fuoss–Onsager–Skinner (FOS) equation. The values of the limiting equivalent conductance, Λ0, the association constant, KA, and the distance of ion-size parameter [Formula: see text] are computed from these data. A better fit of the conductance data was provided by the F78 equation. Ion–solvent interactions and effective sizes of tetraalkylammonium ions are also discussed in order to understand the magnitude of the ionic association. The overall association behaviour of these salts has been found to increase with decrease in dielectric constant of the medium.

Chromatographic Determination of Thermodynamic Acid Dissociation Constants of Tetracycline Antibiotics and Their Epimers

2019 ◽  
Vol 57 (8) ◽  
pp. 745-750
Author(s):  
İlkay Konçe ◽  
Ebru Çubuk Demiralay ◽  
Hülya Yılmaz Ortak
Keyword(s):  
Experimental Data ◽  
Dissociation Constant ◽  
Binary Mixtures ◽  
Dissociation Constants ◽  
Reversed Phase ◽  
Acid Dissociation ◽  
Acid Dissociation Constant ◽  
Chromatography Method ◽  
Ph Values

Abstract The presented study describes the development of reversed-phase liquid chromatography method using a core-shell particle column with a pentafluorophenyl stationary phase for the dissociation constant (pKa) determination of the tetracycline group antibiotics (tetracycline, oxytetracycline, chlortetracycline) and their epimers (4-epitetracycline, 4-epioxytetracycline, 4-epichlortetracycline). The pH values were measured in the acetonitrile (ACN)–water binary mixtures, used as mobile phases, instead of in water and take into account the effect of the activity coefficients. Thermodynamic acid dissociation constant (pKa1) values of studied antibiotics and their epimers were calculated using retention factor (k) at different mobile phase pH values in studied binary mixtures with ACN percentages of 20, 25, 30 and 35% (v/v). Experimental data were analyzed by using an Origin 7.0 program to fit experimental data to the nonlinear expression derived. From calculated pKa1 values, the aqueous pKa values of studied compounds were calculated by different approaches and these values were compared.

Effect of solvent on the ion-pair dissociation constant of tetramethoxybenzene cation radical ion pairs

1980 ◽  
Vol 84 (23) ◽  
pp. 3028-3030 ◽  
Author(s):  
Ignacio J. Ocasio ◽  
Paul D. Sullivan
Keyword(s):  
Dissociation Constant ◽  
Ion Pairs ◽  
Cation Radical ◽  
Ion Pair ◽  
Effect Of Solvent

Modeling of the Kinetic Experiment of Dicyclopentadiene Olygomerization

2014 ◽  
Vol 880 ◽  
pp. 205-211 ◽  
Author(s):  
Alexey Lyapkov ◽  
Vladimir Bondaletov ◽  
Elena Melnik ◽  
Georgy Borisov
Keyword(s):  
Experimental Data ◽  
Catalytic System ◽  
Ion Pairs ◽  
Effective Rate Constant ◽  
Catalyst System ◽  
Effective Rate ◽  
Probable Mechanism ◽  
Raw Material ◽  
Kinetic Experiment ◽  
System Components

Regularities of the dicyclopentadiene cationic oligomerization under influence of the catalytic system AlEt2Cl: TiCl4 in toluene solution were studied. The most probable mechanism of polymerization in this system is the propagation chain on the contact or solvate-separated ion pairs. The effective rate constant of solvation of the catalyst and chain propagation were calculated. The thermal oligomerization effect and heat of the catalyst system components solvation are determined by heat of oligomerization raw material containing dicyclopentadiene. When taking into account the data of both material and thermal balance the experimental data were described adequately.

Osmotic and activity coefficients in dilute potassium chloride solutions at 25 °C

1980 ◽  
Vol 58 (13) ◽  
pp. 1386-1387 ◽  
Author(s):  
Chai-Fu Pan
Keyword(s):  
Vapor Pressure ◽  
Potassium Chloride ◽  
Activity Coefficients ◽  
Size Parameter ◽  
Pressure Data ◽  
Vapor Pressure Data ◽  
Chloride Solutions ◽  
Ion Size ◽  
Robinson Equation ◽  
Existing Data

Osmotic and activity coefficients of dilute aqueous potassium chloride solutions are calculated from the simplified forms of the Stokes and Robinson equation. The hydration parameters in these equations are obtained from the vapor pressure data measured at higher concentration regions and the ion-size parameter is chosen as the sum of the crystallographic radii of the cation and anion of the electrolyte. The results are very satisfactory in comparison with existing data.

scholarly journals Ca2+ buffering in the heart: Ca2+ binding to and activation of cardiac myofibrils

2000 ◽  
Vol 346 (2) ◽  
pp. 393-402 ◽  
Author(s):  
Gerry A. SMITH ◽  
Henry B. F. DIXON ◽  
Heide L. KIRSCHENLOHR ◽  
Andrew A. GRACE ◽  
James C. METCALFE ◽  
...  
Keyword(s):  
Experimental Data ◽  
Dissociation Constant ◽  
Dissociation Rate ◽  
Troponin C ◽  
Cardiac Contraction ◽  
Myofibrillar Atpase ◽  
Dissociation Rate Constants ◽  
Contraction And Relaxation ◽  
Ferret Heart

The measurement of cardiac Ca2+ transients using spectroscopic Ca2+ indicators is significantly affected by the buffering properties of the indicators. The aim of the present study was to construct a model of cardiac Ca2+ buffering that satisfied the kinetic constraints imposed by the maximum attainable rates of cardiac contraction and relaxation on the Ca2+ dissociation rate constants and which would account for the observed effects of 19F-NMR indicators on the cardiac Ca2+ transient in the Langendorff-perfused ferret heart. It is generally assumed that the Ca2+ dependency of myofibril activation in cardiac myocytes is mediated by a single Ca2+-binding site on troponin C. A model based on 1:1 Ca2+ binding to the myofilaments, however, was unable to reproduce our experimental data, but a model in which we assumed ATP-dependent co-operative Ca2+ binding to the myofilaments was able to reproduce these data. This model was used to calculate the concentration and dissociation constant of the ATP-independent myofilament Ca2+ binding, giving 58 and 2.0 μM respectively. In addition to reproducing our experimental data on the concentration of free Ca2+ ions in the cytoplasm ([Ca2+]i), the resulting Ca2+ and ATP affinities given by fitting of the model also provided good predictions of the Ca2+ dependence of the myofibrillar ATPase activity measured under in vitro conditions. Solutions to the model also indicate that the Ca2+ mobilized during each beat remains unchanged in the presence of the additional buffering load from Ca2+ indicators. The new model was used to estimate the extent of perturbation of the Ca2+ transient caused by different concentrations of indicators. As little as 10 μM of a Ca2+ indicator with a dissociation constant of 200 nM will cause a 20% reduction in peak-systolic [Ca2+]i and 30 μM will cause approx. 50% reduction in the peak-systolic [Ca2+]i in a heart paced at 1.0 Hz.

scholarly journals Consistent force field for metalloporphyrins

2010 ◽  
Vol 75 (12) ◽  
pp. 1671-1683
Author(s):  
Ljubica Andjelkovic ◽  
Sonja Grubisic ◽  
Ivana Djordjevic ◽  
Matija Zlatar ◽  
Svetozar Niketic ◽  
...  
Keyword(s):  
Experimental Data ◽  
Force Field ◽  
Molecular Mechanics ◽  
Metal Ion ◽  
Graphite Layer ◽  
Normal Coordinate ◽  
Out Of Plane ◽  
Equilibrium Structures ◽  
Ion Size ◽  
Consistent Force Field

Molecular mechanics (MM) calculations to analyze the puckering of metalloporphyrins isolated and adsorpted on a graphite layer (0001) as a function of metal ion size and the peripheral substitution are presented. The Consistent Force Field (CFF) program was used with new parameters for metalloporphyrins, which included an out-of-plane bending function. Normal-coordinate Structural Decomposition (NSD) analysis was performed on the equilibrium structures obtained by MM calculations. The conformers were also stereochemically characterized and compared with available experimental data and with conformers obtained in a previous MM study.

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